The control system of the ITER vertical stabilization converter

The paper describes the control system of the International Thermonuclear Experimental Reactor (ITER) Vertical Stabilization converter, which has been optimized to achieve the best performance in terms of response time. The VS converter is rated for 8 kV no load output voltage and 22.5 kA maximum output current; it is based on two identical basic units connected in series, each made of two identical subunits connected in parallel. The converter four quadrant operation is first described, and the undesired current unbalance between the converter subunits, due to fast voltage transients, is discussed; then the design criteria and the regulator structure to avoid current unbalances are described. Finally, the simulation results of the complete circuit operation in the worst conditions are reported to evaluate the converter performances. The results show that also in these conditions the specified performances are satisfied, while in a wider operating region the dynamic behavior is much better than requested. Current unbalances are avoided during the inversion phase; it is also pointed out that transients in the system can be controlled without chokes, which therefore can be avoided reducing the system cost.